How CAN works in the U2C DC/DC Converter
Here is the way that CAN works for the U2C:
Pins 1-4 (CAN LOW) are connected internally inside the U2C.
Pins 2-5 (CAN HI) are also connected internally inside the U2C.
Pin 6 (CAN Term 1) and Pin 7 (CAN Term 2) are each connected to a 60Ω resistor
and then to ground thru the same 1μF capacitor. All of that is inside the U2C.
This design allows the U2C great versatility.
If there are more “boxes” downstream in the car that need CAN lines, then our
second pair of CAN lines would be continued to that box. For instance, if the
incoming CAN lines in the vehicle harness were connected to Pins 1 and 2, then
the outgoing lines that continue to the next box would be 4 and 5.
If, however, there are no more “boxes” to be connected to the CAN stream, then the
second pair of our CAN pins would be connected to Pin 6 (CAN Termination 1) and
Pin 7 (CAN Termination 2). For instance, to expand on the first example, if your
incoming CAN lines in the vehicle harness were connected to Pins 1 and 2, then
Pins 4 and 5 would be connected to Pins 6 and 7.
If you decide you need to connect Pins 4 and 5 to Pins 6 and 7, it won’t matter
which way you hook them up. As I described above, Pins 6 and 7 are both the
same inside the U2C.
To verify that you have made this connection correctly, use a DMM to measure
across Pin 6 and 7. You should read 60Ω’s. Why? Because the two 60Ω resistors in
our box are in parallel with two other 60Ω resistors in the CAN transmitter (it’s an
impedance match).
The Transceiver that is used on our U2C board is an Infineon part. The part
number is TLE 6250G - V33. It's a very robust, high speed device that has worked
extremely well in the U2C.